A typewriter as well as other forms of serial impact printers typically includes provision for relative motion between the impact means and the print receiving means so that the characters may be printed along a line. Commonly, of course, in older style typewriters, the print receiving medium is moved with respect to the character elements which remain stationary. That is, the platen and paper move with respect to the frame of the machine while the character elements are substantially fixed. More commonly today in the design of typewriters and serial impact printers, the print elements are moved with respect to the platen. This is particularly important in certain typewriters and printers associated with word processors which are required to operate at very high speeds and to print in an automatic memory mode. In order to further increase the speed of such printers, it is desirable to reduce the inertia of all moving parts so as to require less force for starting and stopping these moving parts in operation, the mechanical operations being a limiting factor in the speed of such machines. Therefore, it has been found desirable to move the print element rather than the platen with respect to the frame of the machine, since the print element in general may be of lighter weight.
It has also been found desirable that the printing ribbon which passes between the print receiving means and the character elements be stored in a stationary position with respect to the frame of the machine so that this too allows a reduction in the inertia of moving parts. This has been accomplished as disclosed in copending applications Ser. No. 833,270, filed Sept. 14, 1977 and Ser. No. 833,257 filed Sept. 14, 1977 now abandoned by providing flexible leaders which guide the printing ribbon between a stationary ribbon cartridge and movable print point. However, in order for these leaders to function properly, it is important that the leaders bend in only one direction (i.e., no reverse bending) so as to assure that the ink side of the ribbon will not contact the leader where the leader forms an enclosed channel. It is also important in some instances to assure that the leader has a uniform bending radius.